relax SVN archive

Initialised the molecule user function GUI element class.

Created the UF_window base class for all user functions requiring generic windows.

Renamed build_menu_sub_item() to _build_menu_item().

Sub-menus are now supported in the main relax menu bar.

The 'User functions->molecule->add' sub-menu item has been added, but is not yet functional.

Fix for the new _create_sub_menu() method.

Shifted out the generic sub-menu building code from _user_functions() to _create_sub_menu().

Shifted the 'user function' sub-menu construction into _user_functions().

Shifted out the GUI main menu bar into its own module.

Improvements to the unfolded molecule icon - there is now residual structure!

The molecule icon changes from folded to unfolded as the tree is opened and closed.